Saline Sonogram (SIS)

A saline sonogram (saline infusion sonography/SIS/sonohysterography) is a procedure where a small amount of sterile saline (5–15mL) is gently injected into the uterine cavity through a thin catheter while performing a transvaginal ultrasound scan. The fluid outlines the cavity walls, making it much easier to detect polyps, submucosal fibroids, adhesions, and uterine septa that are invisible or unclear on standard TVS.

Before IVF, the uterine cavity must be clear of lesions that impair embryo implantation. Studies show that intracavitary pathology (polyps, submucosal fibroids, adhesions) reduces IVF implantation rates by 30–50%. A saline sonogram identifies these lesions in 10–35% of women who appear to have a normal cavity on standard TVS. Once identified, hysteroscopic removal of polyps or fibroids before IVF significantly improves live birth rates — the benefit is highest for polyps (doubles live birth rate per JAMA 2023 RCT).

No — they serve different purposes. Saline sonogram (SIS): evaluates the uterine cavity using TVS + saline; excellent for detecting intracavitary lesions (polyps, fibroids, adhesions); does not reliably assess tubal patency. HSG (hysterosalpingography): X-ray contrast through the cervix; primarily assesses tubal patency; also shows cavity outline but lower sensitivity for soft tissue lesions. HyCoSy/HyFoSy (ultrasound-based): can assess both cavity and tubal patency in one visit — increasingly replacing separate SIS + HSG.

Most women experience mild to moderate cramping during a saline sonogram — similar to strong period pain for 2–5 minutes when the catheter passes through the cervix and when saline is injected. Pre-medication with ibuprofen 400mg 1 hour before reduces discomfort significantly. A small balloon-tipped catheter (prevents backflow) may cause slightly more cervical discomfort than a non-balloon catheter. Severe pain is uncommon and should prompt the procedure to stop and causes re-evaluated.

If an endometrial polyp is found on SIS, the recommended management before IVF is hysteroscopic polypectomy — surgical removal under direct visualisation (outpatient or day case, usually under light sedation or general anaesthesia). A confirmatory SIS or TVS is performed 4–6 weeks later to confirm the cavity is clear. IVF cycle proceeds once the cavity is confirmed clear. Removing the polyp before IVF doubles the live birth rate in women with polyps >10mm (JAMA 2023 RCT evidence).